Powder injection moulding (PIM) is a manufacturing technique in which a liquid compound of polymeric binder and metal carbide or ceramic powders is injected by an injection moulding machine into a closed mould at high pressure. The method combines the advantages of plastic injection moulding, such as good mould filling and the ability to manufacture complex shapes, with the possibility of using hard and high-strength materials, such as cemented carbides and cermets as component material. This makes powder injection moulding a suitable method for manufacturing strong and abrasion resistant components having narrow tolerances or complex shapes. For example various types of cutting inserts or components for the automotive industry.
However, powder injection moulding has some limitations when it comes to components with designs including through holes, for example, cutting inserts with through holes for fasting screws or fastening systems.
Due to the characteristics of the PIM-compound, it is preferred to avoid meeting flow fronts of PIM-compound in the mould since a weakening weld line may result in the solidified component in the area where two flow fronts meet. When manufacturing components with through holes by powder injection moulding it is therefore preferred to fill the mould radially around or along the core which defines the through hole in the component. Thereby the component will remain dimensionally stable without getting distorted as it might be with e.g. a single gate positioned at one side.
WO2009139700A1 describes a moulding tool and a method for manufacturing a cutting insert having a through hole by powder injection moulding. To avoid meeting flow fronts in the mould, the moulding tool in WO2009139700A1 is arranged such that PIM-compound is injected directly onto the end surface of the core. This results in that the PIM-compound is deflected radially by the end surface of the core and the mould is filled evenly around the core.
However, the conventional practice results in that, after completed filling and solidification, a plug of solidified PIM-compound remains in the through hole of the component. To clear the through hole, the plug needs to be removed in a subsequent machining operation. Such machining and the necessary handling of the components result in high production costs when manufacturing components with through holes by powder injection moulding.